Field of the Invention
The field of the present invention is forging metallic or other suitable materials in accordance with cold, warm, or hot forging operations.
Background
As is well known, forging is a process by which a product is formed from a metallic or other suitable materials into a particular or desired shape. During the forging process, metallic materials, such as aluminum, may be subjected to conventional cold, warm, or hot forging operations to force the materials to assume a particular shape.
Although there are many different forging techniques, one particular type utilizes a die set including a holding portion, within which a workpiece is disposed. A punching portion of the die set is dropped down to press against the workpiece and force it to flow into a guiding portion of the die set and to assume a particular shape within the guiding portion. During this type of conventional forging process, the die set suffers damage. Also, there is stagnant buildup of dead material from abnormal flow of material.
FIG. 1a further illustrates the manner in which such a conventional forging process can generate damaging cracks. A workpiece W is disposed within the holding portion 4'(2') of the die set 2', which is integrally formed with the guiding portion 5'(2') of the die set 2' as a single unit. The punching portion 3'(2') is pressed against the workpiece W to accelerate the plastic deformation phase of the workpiece. This exerts extreme pressure on the die set 2'. As the workpiece W is pressed down, the portion of it that contacts an area of the guiding portion 5'(2'), as indicated by reference letter W1, pushes downward in the direction of the pressing action, as illustrated by the vertical arrows in Figure la. At the same time, the portion of the workpiece that contacts the wall of the holding die 4'(2'), as indicated by reference letter W2 pushes outward, exerting pressure on the holding die 4'(2') in a direction illustrated by the horizontal arrows in FIG. 1a. Consequently, at the corner C where the holding portion 4'(2') transitions into the guiding portion 5'(2'), forces are simultaneously exerted in two different directions, perpendicular to each other. The diverging forces at the corner C in this integrally formed configuration cause the die set 2' to tear and cracks to occur at the corner C. When such cracks occur, the die set 2' is damaged and rendered ineffective, requiring replacement.
To overcome this problem, in another configuration, the holding portion 4'(2') and the guiding portion of the die set are formed separately. Such a configuration is illustrated in FIG. 1b. This configuration is further reinforced from the outside to resist cracks. While this configuration, addressed the problem of alleviating the forces at the corner C that caused the cracks, it gave rise to yet other problems. For instance, as the punch die 3' presses down on the workpiece, there is a tendency for the workpiece material under pressure to escape into any space or clearance that may exist between the holding die 4' and the guiding die 5'. The material slipping into the clearance between the holding die 4' and guiding die 5' results in the formation of burrs. Gradually, with time and usage, the seepage increases, causing buildup of dead material that serves as a wedge, prying the holding die 4' away from the guiding die 5'. Additionally, the formation of burrs destroys the layer of lubricant that is applied on the workpiece prior to commencing the forging process. Once the lubricant is destroyed, the material is further obstructed from flowing along its intended path down into the guiding portion 5'.
In addition, as the workpiece W presses down along the inner walls of the holding die 4', material collects at the corner E where the holding die 4' and the guiding die 5' meet. The arrows in Figure lb illustrate the sluggish and abnormal flow patterns along the corner E, resulting in buildup of material at that location that ultimately remains there and stagnates. The stagnant material is essentially dead metal (indicated by reference numeral D) that prevents products from forming properly.
In a further attempt to address this problem and to prevent the buildup of dead material, the guiding die 5' is curved at the corner E, to provide a rounded surface, instead of sharp corners where the dead metal D once remained. But again, such a configuration not only resulted in the same problem where burrs occur, but, the same bidirectional forces at the curved portion also resulted, causing cracks.